I created a table Lectures which has 2 fields LectureID (primary key) and LectureName. I also created a table Persons which has 5 fields, Person ID (primary key) and 4 others which describe that person.

I don't know how to "remember" the fact that a person was on a lecture. I definitely need to remember it so I can use it later.

If you want to make any type of the database either its simple or the complicated then the data tables and the queries are the most important thing that you have to make a good command over it.After that you will make all type of complicated database also.